We might not be able to remember every stressful episode of our childhood.
But the emotional upheaval we experience as kids — whether it's the loss of a loved one, the chronic stress of economic insecurity, or social interactions that leave us tearful or anxious — may have a lifelong impact on our health.
In fact, a study published this week in the Journal of the American College of Cardiology indicates that emotional distress during childhood — even in the absence of high stress during adult years — can increase the risk of developing heart disease and metabolic disorders such as diabetes in adulthood.
"We know that the childhood period is really important for setting up trajectories of health and well-being," explains Ashley Winning, an author of the study and postdoctoral research fellow in social and behavioral sciences at the Harvard T.H. Chan School of Public Health.
To assess the connection between childhood stress and the risk of disease, Winning and her colleagues analyzed data from the 1958 British Birth Cohort Study, a long-running study that documented the diets, habits and emotional health of thousands of British children born during the same week that year.
As the children entered school, the classroom became the laboratory for observation.
"Teachers collected a lot of information — assessing signs and symptoms of distress," Winning explains. "The teachers were checking off [answers to questions such as]: 'Was this child tearful or sad?' " Teachers completed a 146-item assessment.
Teachers evaluated each child at ages 7, 11 and again at 16. After that, as the participants grew older they completed their own assessments of the stress in their lives at ages 23, 33, and 42.
When the participants turned 45, they underwent a biomedical assessment to measure markers of metabolic and cardiovascular health — as well as immune function.
Using these data from 6,714 participants, Winning and her colleagues analyzed the relationship between stress and the risk of various chronic diseases.
"Not surprisingly, those with persistent distress — so, both in childhood and adulthood — had the highest risk," Winning says.
But here's the surprise: Even the adults who had lower distress levels were at higher risk of chronic illness if they had experienced higher levels of distress during childhood.
"It's very interesting that early-life experiences seemed to be such an important predictor [of disease risk]," says Aric Prather, a research psychologist in the department of psychiatry at the University of California, San Francisco. Though the study can measure only correlation, not causation, it dovetails with other findings. And the large number of people it tracked for many decades make its findings worth paying attention to, scientists say — and worth following up on with other kinds of research.
Prather, who also studies the links between psychology and immunity, says the mechanisms by which early-life experiences influence health are complicated and not yet completely understood.
"There's certainly growing evidence that there may be some biological embedding that takes place," Prather says.
In other words, it's possible, he says, that when people experience early-life stress "it actually changes something about them biologically." Stress may influence how genes get switched on or off, for instance, or may initiate some other physiological effects.
There's still a lot to learn, but this much is clear, Prather says: "The mind and the body are much more tightly related than we used to believe."